It is known that switching systems can be constructed from a combination of AWGs and tunable wavelength convertors (TWCs) and the potential for the cyclic AWG in optical switching has been recognized in recent years. Ye et al (IEEE/ACM Transactions on Networking, VOL PP, Issue 99, Page 1, February 2014) describe the use of AWGs in Clos-type optical switches and other architectures and Ngo et al (Proceedings 23rd Conference of IEEE Communications Soc, 2004) have illustrated AWG switch architectures that are rearrangeably non-blocking and strictly non-blocking. Lucerna et al (AWG-Based architecture for optical interconnection in asynchronous systems in 2011 IEEE 12th International Conf on High Performance Switching and Routing) have discussed the problem of cross-talk in high port count AWGs and proposed a method of overcoming this by scheduling packets. In all such systems there must be an efficient means of optical wavelength conversion and the wavelength must be tunable. Pallavi and Lakshmi (I. J. Information Technology and Computer Science, 2013, 04, 30-39) have discussed optical packet switches constructed with AWGs where there is central control over the whole packet switch. U.S. Pat. No. 8,792,787 describes optical packet switches involving TWCs and AWGs combined in layers and in 2 or more stages.